1. Field of Industrial Application
The present invention relates to a tone synthesizer suitable for simulating acoustic musical instruments whose pitch changes according to the position of the lips of the player.
2. Prior Art
There are methods for synthesizing tones of a natural musical instrument by applying a model obtained by simulating the sound mechanism of natural musical instruments. Especially for the most basic model of a musical wind instrument, like a clarinet, a closed loop structure model is known for connecting non-linear amplification elements simulating elastic characteristics of the reed with bidirectional communication circuits simulating a resonance pipe. In this model, the signal coming from the non-linear amplification element is output, and after being added to the retreat wave signal, this signal is input into the bidirectional communication circuit as a progressing wave signal. Next, this progressive wave signal is reflected at the terminal part of the bidirectional communication circuit and transmitted in the opposite direction of the bidirectional communication circuit. After that, the reflected wave signal is added to the progressive wave signal and fed back to the non-linear amplification element (driving circuit).
Thus, the propagation of the air pressure wave in the wind instrument can be truly simulated by the closed loop circuit consisting of the non-linear amplification element and the bidirectional communication circuit.
Furthermore, in real wind instruments, holes for pitch operation, in other words "tone-holes", are provided; models simulating wind instruments including such tone holes are also known. In this model a signal progressing circuit which is called a signal scattering junction (hereafter referred to as "junction") is inserted between all bidirectional communication circuits, each corresponding to a tone hole. For each input signal from the adjacent bidirectional communication circuit, calculation processing, such as coefficient multiplication, is done by each junction, and the calculation result is supplied to the adjacent bidirectional communication circuit. The multiplication coefficients and the like in this calculation processing are changed according to the opening and closing condition of the tone hole.
In this case, the signal fed back to the non-linear amplification element becomes the sum total of the components returned in each junction. Furthermore, as described above, because the multiplication coefficients used for calculating in the junctions are changed according to the opening and closing condition of the tone hole, finally, the transmission frequency characteristic of the bidirectional circuit side, when seen from the non-linear amplification element, is changed according to the opening and closing condition of the tone hole.
This transmission frequency characteristic becomes a characteristic of a plurality of peaks having resonance frequencies at a frequency (fundamental tone) corresponding to the time delay of the output signal of the non-linear amplification element returned in the junction corresponding to the tone hole of the opening condition until fed back to the non-linear amplification element and all the frequencies (harmonic tones) of approximately multiple integers thereof. This type of technique was officially disclosed in, for example, Japanese patent application laid open number Sho 63-40199.
Since in the above mentioned art, the main objects for simulation were woodwind instruments, no functions were provided which made it possible to produce a tone based on parameters such as the positioning of the player's lips, force conditions, and stress conditions (conditions of the muscles around the mouth), neither did they provide a construction for detecting the stress condition of the lips. Therefore, in the above-described art, it was extremely difficult to simulate brass instruments where tones are in part decided by the degree of strain of the lips.